Experimental Research On Z-source Inverter For Electric Vehicle Motor Drive

New energy vehicles have become the new direction of global automotive industry.In the application of electric vehicles, a Buck-Boost converter is usually needed to boostthe car power voltage for the inverter to drive the motor. As a new power converter,Z-Source inverter can achieve boost features with single-stage structrue and is suitablefor all forms of dc power such as fuel cell, battery and ultracapacitor, which meetselectric vehicle applications very well. The system of Z-Source inverter for electricvehicle motor drive is designed and related issues are studied in this paper.Space Vector Pulse Width Modulation(SVPWM) is widely used in motor control forelectirc vehicles for its advantages of high voltage utilization, low current harmoniccontent and good sinusoidal output voltage. The key of SVPWM for Z-Source inverter ishow to insert shoot-through state to achieve boost feature. By studing the distribution ofshoot-through state, the causes of maximum inductor current ripple for two existingmodified SVPWM control are explained theoretically and experimentally. On this basis,two novel modified SVPWM control methods are proposed to decrease inductor currentripple and the volume of inductor by optimizing the shoot-through state distribution.Inductor current ripple and inductor design of four modified SVPWM control methodsare compared with a certain example.Snubber circuit is an important part of the main circuit of motor drive, whichprotects the power devices. The dc-link voltage of Z-Source inverter is discontinuouswith shoot-through zero voltage and the peak voltage is higher than dc supply voltage. Sothe working process of snubber circuit is different with that of conventional inverterwhich needs more protection when Z-Source inverter is used in electric vehicles. Thecommutation process of Z-Source inverter is analyzed in detail and the variation ofvariables is summarized. On this basis, comparative experiments show the difference ofbuffering effect between different snubber circuit. Specials of Z-Source inverter snubbercircuit is analyzed.Finally, the control system of Z-Source inverter for electric vehicle motor drive isdesigned. Combined with electric vehicle applications, bi-directional Z-Source inverter isused to achiece torque control of PMSM.